Coherent π0 electroproduction on 4He in the Δ region

Coherent π0 electroproduction on 4He was studied using the internal target facility of the AmPS electron storage ring at NIKHEF. This 4He(e,e14Heπ0 experiment is the first on exclusive π0 electroproduction on a complex nucleus. The experiment was performed at a luminosity of about 1033 cm−2s−1 with a stored beam of about 150 mA 676 MeV electrons and a 4He gas target of 1015 atoms/cm2. The observation of neutral pions was avoided by detecting in coincidence with scattered electrons the recoiling 4He nuclei with a dedicated detector. A clear signature for π0 knockout was achieved and the differential cross sections were measured as a function of the π0 CM-angle over the full Δ-resonance region at two values of Q2 of 0.07 and 0.15 (GeV/c)2.